1. Field of the Invention
The present invention relates to a polymer for positive photoresist and a chemical amplification positive photoresist composition comprising the same. More particularly, the present invention relates to a polymer for positive photoresist, which gives a resolution as small as quarter-microns and shows superior adhesiveness to any substrate in addition to being developable without changing the concentration of developing solution and to a chemical amplification positive photoresist composition.
2. Description of the Prior Art
The high integration of semiconductor devices has been partly, but critically based on a significant advance in lithography. For example, ultra-fine patterns as small as quarter-microns in size are required for the fabrication of ultra-LSI. Accordingly, the light sources used to form the fine patterns become shorter and shorter in wavelength, for example, from g-line to l-line and deep uv light, further to KrF excimer lasers, and finally to electron beams.
Since the photoresists utilizing g-line or l-line, which belong largely to novolak-quinones, show large absorption peaks at the wavelength range of deep uv or KrF excimer laser, such a fine pattern is not obtainable therefrom. Thus, there was a strong demand for a material which little absorbs the light belonging to such wavelength ranges. In response to the demand, active research has been directed to the development of the chemical amplification photoresists based on polyhydroxystyrene derivatives, which are smaller in absorbance at such ranges than are novolak-quinonediazides. The chemical amplification photoresists based on polyhydroxystyrene derivatives, however, were found to be unsuitable for utilizing an ArF excimer laser since they show a large absorbance at the wavelength of the light source (193 nm).
As an alternative, polyacrylate derivatives appeared to avoid the absorption. Polyacrylate derivatives show little absorbance at 193 nm but are inferior to novolak resins or polyhydroxystyrene derivatives in etch resistance. In the last few years, much effort has been made to overcome the disadvantage, including the introduction of alicyclic derivatives in polyacrylate (Proc. SPIE, 1996, 2724, 365) and cycloolefin derivatives into the main chain of base resin (Proc. SPIE, 1996, 2724, 355). These methods, however, have not yielded satisfactory results, such as fine patterns as small as quarter-microns.
Collectively, the conventional chemical amplification photoresists have significant disadvantages of being high in absorbance at the short wavelength ranges of deep uv, KrF excimer laser or ArF excimer laser so as not to yield satisfactorily fine patterns as small as quarter-microns, in addition to being poor in etch resistance.